The AI seems to struggle when it comes to using AoEs, particularly resizable ones. Seto, for instance, doesn't seem to target anything with its Isenshi, while the following skills (admittedly applied to custom mobs) are used, but do not target anyone, thus failing to produce any effect:

*Flamethrower*Kagekiri*Hirazuki*Bullet Shred

On a semi-related note, while the Firthrower weapon can still be perfectly used by Monsters, it seems to make them forget about moving entirely.